This invention relates to color picture tubes having apertured mask electrodes therein, and particularly to mask construction that reduces mask-frame assembly thickness.
The most common type of color picture tube for producing a color image is the shadow mask type cathode-ray tube. In this tube type, a plurality of convergent electron beams are projecting through a multi-apertured color selection shadow mask to a mosaic screen. The beam paths through the mask are such that each beam impinges upon and excites only one kind of color-emitting phosphor on the screen. Generally, the shadow mask is attached to a rigid frame, which in turn, is suspended within the picture tube envelope.
Usually, a shadow mask type cathode-ray tube is constructed in two parts comprising a rectangular panel or cap portion and a funnel and neck portion which are eventually sealed together. The shadow mask-frame assembly is supported within the cap by a plurality of springs. In the past, the mask-frame assembly was confined entirely within the cap. However, because of recent improvements in shadow mask design which included increasing the curvature of the mask, the thickness of the mask-frame assembly is so great that a portion of the mask-frame assembly in these newer tubes now extends beyond the protective sidewalls of the cap. This is disadvantageous since the cap must be handled and moved on several occasions during manufacture so that the risk of damage to the mask-frame assembly is greatly increased. Therefore, new designs are necessary to provide reduction in mask-frame assembly thickness so that the entire assembly will fit within the tube cap.